The invention relates to an apparatus for applying light to a site to be treated on a wall of a vessel in the human or animal body, in particular for laser welding of two vessels to one another, having a light-feeding instrument that guides light generated by an extracorporeal light source to the site and radiates it onto the latter.
A general case of application of such an apparatus consists in the application of light to a site to be treated on a wall of a vessel, in order to heal a pathological state, for example a tissue change or a rupture in the vessel wall, at this site.
A special case of application of the apparatus mentioned at the outset to which the following description relates without being restricted thereto is the application of such an apparatus for laser welding of two vessels to one another in order to join the latter to one another end to end or else end to side such that a T-shaped join is produced. Vessels are to be understood as blood vessels such as veins or arteries, or else in the wider sense generally as hollow organs. Such a join of two vessels to one another is required, for example, when a vessel has been ripped open because of injury or because of a surgical resection, or in order to join two vessels opening into one another so as to create a new vessel path or to reconstitute an original one.
In the case of conventional methods for joining two vascular stumps to one another end to end, which is also denoted as anastomosis, the two vascular stumps have been joined to one another by means of conventional suture methods. Such suture methods are, however, time-consuming surgical methods that require experience and skill on the part of the surgeon. Furthermore, when sewing together two vascular stumps there is the risk that an aneurysm, that is to say a weakening of the vessel wall with attendant outward sagging of the vessel wall, will develop at the suture site, or that foreign-body reactions will occur because of the suture material. Moreover, suture joins can frequently only be produced in the case of vessels in open, that is to say invasive operations.
The development of laser surgery has now rendered it possible to replace suture joins by laser welding. It has emerged that laser light of suitable wavelength and suitable power can also be used to “fuse together” tissue of vessels. Successful experiments have already been carried out in vitro for the purpose of welding two vascular stumps end to end. The advantage of the laser treatment as against the conventional suture techniques consists in a lower time outlay and in the avoidance of foreign-body reactions owing to suture material. Moreover, laser welding techniques can also be carried out endoscopically by means of small incisions, that is to say in a minimally invasive fashion.
Although the mechanisms of the laser welding process are not yet completely understood in the case of vascular tissue, it is surmised that the laser light that heats the tissue locally leads to a coagulation of proteins and thus to an anastomotic joining of vascular stumps. However, vessels welded with laser light frequently exhibit insufficient stability of the join that can lead to leaks under the strain of the blood pulsating in the vessel, or even to a complete rupture of the join.
It has therefore been proposed to apply to the junction in advance of the welding a biological solder such as fibrin or albumin in liquid or solid form which penetrates into the tissue to be welded and acts as adhesive during welding. In addition, these are mixed with a chromophore, as absorber, the absorption maximum of which is at the wavelength of the laser light used, in order to launch the laser light optimally into the solder and to release the laser energy there.
A problem is posed, however, by the application of the light in vivo to the site to be treated on the wall of the vessel. When applying the light from the outside of the wall of the vessel, it proves to be difficult to treat such a site on the wall of the vessel that is situated on the side of the vessel averted from the incision. Particularly in the case of laser-aided anastomosis, in which two separated vessels are to be welded to one another, the light-feeding instrument would need to have on the light-exit side an end that can be guided over an entire circumference around the outside of the wall of the vessel. This could be performed, for example, by forceps whose distal end has a cylindrical gripper that can be spread and with the aid of which the vessel is embraced as by forceps, and in which case the light exits circumferentially on the inside of the grippers. However, there is the risk in this case of the vessels collapsing during welding, with the result that the vessel is no longer open for the passage of blood after production of the welded join. Moreover, introducing such an apparatus into the body may require an open invasive operation.
It is therefore the object of the invention to create an apparatus of the type mentioned at the beginning with the aid of which the light can be applied in a minimally invasive way to the site to be treated on the wall of the vessel, and with the aid of which collapse of the vessel upon application of the light is avoided.